When using remote to open door, front lights do not flicker.
and when locking doors signal no longer heard
Change the key fob battery
I don’t see how the state of the FOB battery plays into it but here’s some excerpts from your owner’s manual that may help:
Notice it says if one of the doors are open, it won’t alert. It may be that one or more of your door closed switches is malfunctioning and the BCM thinks they are open. However, a more likely scenario is the following:
See the last section describing how to disable the alert feature-
Maybe you just held the button too long once and disabled that feature? Try re-enabling it as described.